Indicating and alarm system



May 11, 1965 c. M. wHlTBY ETAL 3,183,497

INDICATING AND ALARM SYSTEM Filed 0G11. 27. 1961 United States Patent 3,183,497 HNDECATNG AND ALARM SYSTEM Clyde M. Whitby, Beltsville, and Robert R. Fontaine, Riverdale, Md., assignors to ACE*1 Industries, New York, NX., a corporation of New Jersey Fiied ct. 27, 1%1, Ser. No. 14S-,071 4 Claims. (Cl. 340-213) The present invention relates to an indicating and alarm system for supervising a plurality of circuits.

In many applications it is desirable to supervise a large number of circuits and identify any one in which a ault or other condition occurs, and also to provide an alarm when such a fault occurs. The apparatus for accomplishing these results when a large number of circuits are to be supervised has, in the past, been complex.

t is, of course, desirable to reduce the complexity to a minimum. lt is accordingly an object of the present invention to provide a relatively simple circuit arrangement for identifying .any one of a large number of circuits in which a predetermined condition occurs and to operate an alarm upon such occurrence.

lt is a further object of the invention to provide in a simple manner an indication of a predetermined circuit condition and to maintain the indication only for the duration ofthe condition.

in addition another object of the invention is to provide a simple alarm system on the output of chopper stabilized D.C. amplifiers which may either be continuously reset so the disappearance of the trouble results in disappearance of the alarm indication or which may be reset at the discretion ofthe system operator.

It is still another object of the invention to provide a cold cathode glow tube circuit which operates an alarm circuit in response to a trigger signal and identifies the trigger signal.

Other objects and advantages of the invention will become fully understood from the following description and the drawing, in which:

The figure is a circuit diagram of a preferred embodiment of the invention.

The drawing shows a system for monitoring a plurality of circuits in which a faulty condition may occur and includes means for identifying the circuit in which the fault occurs and for operating a relay to close an alarm circuit when the fault occurs. INeon glow discharge tubes il to le of the cold cathode type each include a lontrol electrode iS. Typical tubes are General Electric type NE 77. They have the characteristic that when a sufficient voltage of about 150 volts is applied between the outer el ctrodes, the tube can be fired by the application to the control electrode of a positive voltage .of about 100 volts. The tube continues to discharge after being fired until the voltage across the outer electrodes fall below the ionization potential. Capacitor 20 is connected between anode 21 and control electrode 1S and another capacitor 22 is connected between the control electrode and cathode 23 of each tube. Rectified pulses having a peak voltage of about 170 volts are applied across outer electrodes 21 and 23 of all tubes by an unfiltered full-wave bridge rectifier 24 connected to a source of alternating voltage at terminals 25. One terminal of the bridge rectifier 24 is joined to all cathodes 23 by conductor 26 and the other side of the rectier is connected to all anodes 21 through relay winding 27 and resistors 28, which are individual to each tube. Relay winding 27 is shunted by capaictor for reducing chatter. lf it is desired to provide an electrical latch or hold on the system, the 170 volt peak unfiltered voltage from bridge rectifier 24 can be replaced by 170 volt unfiltered D.C. through switch 54. Thus the tubes il "ice to 16 will not extinguish after the fault is removed unless the system operator breaks the anode circuit using switch 54.

A biasing voltage of about 70 volts D.C. is supplied through a connection 30. and resistors 3l and 32 to control electrodes i8. The biasing voltage is positive and places the control electrodes at a potential approximately one-half of the triggering potential. Control electrodes 1? are also connected individually to the circuits which are to be monitored. Each of these monitored circuits has an input 34 to 39. In a particular embodiment of the invention, these inputs were the error signals at the input grid of D.C. amplifiers. The error or input voltages at 3ft-39 are applied to trigger pulse sources 40 to 45 which `feed positive pulses through capacitors 46 and then through resistors 32 to control electrodes 18. Trigger pulse sources 4h to 45 may be chopper circuits or any other circuits for producing a series of pulses having amplitudes proportional to the input signals applied to devices 40 to l45. In a particular embodiment of the invention, the trigger pulses sources 40 to 4S described above were the chopper stabilization portion of D.C. amplifiers. The stabilization section produced an amplified A.C. voltage proportional to the input grid error voltage. The capacitor 46 then coupled this A.C. voltage to the trouble alarm circuitry described in this invention.

Relay winding 27 actuates grounded armature 48 which is normally open circuited but upon the energization ot' winding 27 closes on contact 52. The latter is connected through a glow tube 5t) or conventional incandescent lamp to terminal 52st ofthe sources of positive voltage. Terminal 52 is also connected through rectifier 53 to a suitable alarm circuit. It is evident then that upon the closing of armature 45 the voltage at terminal 51 causes a discharge in tube Sti and'also completes the alarm circuit, which may have its own source of voltage with one terminal grounded.

The advent of an error signal of sufficient magnitude at one of the terminals 342-39 causes one of the trigger pulse sources to produce a series of positive pulses of sufficient amplitude to trigger the corresponding neon tube lll-16. The tube or tubes receiving triggering pulses of about volts are fired when the anode voltage of the tubes reaches a sufficient value. The tubes then conduct until the anode voltage drops below the ionization voltage, which it does `during each half cycle. This process continues until the triggering pulses fall below the triggering voltage. Tubes ll-l are positioned so as to be visible and so indicate the condition of each circuit being monitored. Thus glow tubes 11-16 show when and where a malfunction or other condition is occurring and the alarm circuit signals the occurrence of any such condition.

ln a practical embodiment of the invention the elements had the following values:

has been described herein it will be evident that many variations thereof may be made within the spirit and scope thereof as defined in the following claims.

What is claimed is: 1. An alarm system comprising: (a) a plurality of gaseous glow discharge tubes having an anode, a cold cathode and a trigger electrode,

mesas? (b) a source of unidirectional voltage pulses,

(c) a relay having a winding connected in series with said source between the anodes and cathodes of said tubes,

(cl) a source of direct voltage connected between said cathodes and trigger electrodes for biasing the trigger electrodes positively relative to the cathodes,

(e) a plurality of sources of triggering signals each connected to one of the trigger electrodes, and

(f) alarm means connected to the contacts of said relay for indicating triggering signals of predetei` mined magnitudes.

2. A system according to claim l including:

(a) a capacitor connecting the trigger electrode to the anode and (b) a capacitor connecting the trigger electrode to the cathode of each tube.

3. An indicating system comprising:

(a) a plurality of gaseous glow discharge tubes having an anode, a cold cathode and a trigger electrode,

(b) a source of voltage pulses having one side thereof connected to all ancdes and its other side connected to `all cathodes of said tubes,

(c) a source of direct voltage connected between said cathodes and trigger electrodes for biasing the trigger electrodes positively relative to the cathodes,

(d) a plurality of sources of triggering signals each connected to one of the trigger electrodes whereby each glow tube is triggered and illuminated to visually indicate the presence of signals from one of said triggering signal sources, and

(e) alarm means connected in series with said source of voltage pulses between said anodes and cathodes.

4. An indicating system comprising:

(a) a plurality of neon glow discharge tubes having an anode, a cold cathode 4and a trigger electrode,

(b) a source of voltage pulses,

(c) including an untiltered full wave rectiiier,

(d) a relay having a winding connected in series with said rectitier between the anodes and cathodes of said tubes,

(e) a source of direct voltage connected between said cathodes and trigger electrodes for biasing the trigger electrodes positively relative to the cathodes,

(f) a plurality of sources of triggering signals each connected between one of the trigger electrodes and the cathodes, and Y (g) alarm means connected to the contacts of said relay for indicating the presence of a trigger signal equal to or greater than a predetermined value,

(l1) the trigger signal having such value beingridentified by the glow of the neon tube to which it is applied.

References Cited by the Examiner UNITED STATES PATENTS 2,321,662 6/43 Dodd 340-213 FOREIGN PATENTS 215,890 7/58 Australia. 858,242 1/61 Great Britain.

NE1L C. READ, Primary Examiner. 

1. AN ALARM SYSTEM COMPRISING: (A) A PLURALITY OF GASEOUS GLOW DISCHARGE TUBES HAVING AN ANODE, A COLD CATHODE AND A TRIGGER ELECTRODE, (B) A SOURCE OF UNIDIRECTIONAL VOLTAGE PULSES, (C) A RELAY HAVING A WINDING CONNECTED IN SERIES WITH SAID SOURCE BETWEEN THE ANODES AND CATHODES OF SAID TUBES, (D) A SOURCE OF DIRECT VOLTAGE CONNECTED BETWEEN SAID CATHODES AND TRIGGER ELECTRODES FOR BIASING THE TRIGGER ELECTRODES POSITIVELY RELATIVE TO THE CATHODES, 